A device of this type is known from WO 97/32182 A1. The known device uses optical coherence tomography to produce cross-sectional images of vessels. In the simplest case, the probe unit of the device features a probe which represents the measuring arm of an interferometer. The probe unit further comprises a reference arm, the optical path length of which can be varied. Light, which features a short coherence length, is fed into both the reference arm and into the measuring arm. The light fed into the measuring arm passes through the probe and is guided to the vessel wall in the region of the probe tip which is located in the vessel to be examined. There the light in different tissue depths is reflected back to the probe tip, detected there and led back through the probe. The light passing back in the reference arm and in the measuring arm is superimposed and supplied to a detector. Modulation means are provided in the reference arm or in the measuring arm, by means of said modulation means the light can be modulated. When the light passing pack from the reference arm and from the measuring arm is interfered in the detector, the intensity detected by the detector is modulated by this modulation. Interference only occurs however when the optical path length of the light in the reference arm and in the measuring arm is approximately the same. By varying the optical path length in the reference arm across several coherence lengths, the photons reflected in each case in a specific tissue depth can result in interference. The probe can be designed such that a cross-sectional profile can be recorded in each instance at a position in the vessel. In the simplest case, this is effected by rotating the probe, with a depth profile being established in each instance in each angular position.
The processing unit arranged downstream of the probe unit then establishes a cross-sectional profile from the measuring signal supplied by the probe unit. As the probe is moved step-by-step through the vessel, the processing unit supplies a series of cross-sectional images one after the other.